Effect of Specimens' Shape and Size on the Determination of Compressive Strength and Deformability of Cement-lime Mortars

This work presents comparative analyses of the effect of specimens' shape and size on the compressive strength and modulus of elasticity of mortars. Mortar mixtures with compressive strength between 5 and 20 MPa were produced. Experimental tests determined the compressive strength of cylinder specimens of (5 x 10) cm and (10 x 20) cm, and also cubic specimens resulted of mortar's flexural strength tests, which use (4 x 4 x 16) cm prisms. The modulus of elasticity of the cylinder specimens was also determined. Cubic specimens' compressive strength was higher than (10 x 20) cm cylinder's compressive strength and lower than (5 x 10) cm cylinder's compressive strength. The dimensions of the cylinder specimens influenced its compressive strength, which was higher for the (5 x 10) cm specimens. However, it did not affect the static modulus of elasticity of the material. Correlations between the results were established and comparisons with different authors' results were made, improving both technological control and characterization of cement-lime mortars.

Keywords:
mortar; specimens; compressive strength; modulus of elasticity

Authorship

Gustavo Henrique Nalon

Universidade Federal de Viçosa - UFV, Av. Peter Henry Rolfs, s/n, Centro, CEP 36570-900, Viçosa, MG, BrazilUniversidade Federal de Viçosa - UFVBrazilViçosa, MG, BrazilUniversidade Federal de Viçosa - UFV, Av. Peter Henry Rolfs, s/n, Centro, CEP 36570-900, Viçosa, MG, Brazil

Roseli Oliveira Guedes Martins

Rita de Cássia Silva Sant'Ana Alvarenga ^**e-mail: rcassia.alvarenga@gmail.com

Gustavo Emilio Soares de Lima

Leonardo Gonçalves Pedroti

White José dos Santos

Universidade Federal de Minas Gerais - UFMG, Av. Antônio Carlos, 6627, Pampulha, CEP 31270-901, Belo Horizonte, MG, Brazil.Universidade Federal de Minas Gerais - UFMGBrazilBelo Horizonte, MG, BrazilUniversidade Federal de Minas Gerais - UFMG, Av. Antônio Carlos, 6627, Pampulha, CEP 31270-901, Belo Horizonte, MG, Brazil.

*e-mail: rcassia.alvarenga@gmail.com

SCIMAGO INSTITUTIONS RANKINGS

Figures | Tables

Figures (5)
Tables (7)

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Figure 1
Flexural and compressive strength tests with (4 x 4 x 16) cm prism specimens.

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Figure 2
Determination of compressive strength and modulus of elasticity of cylindrical specimens.

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Figure 3
Curves of compressive strength - water/cement ratio for different kinds of specimen, for mortars with compressive strength in the range of 5 to 20 MPa.

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Figure 4
Correlations between compressive strength of specimens of different shapes and sizes.

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Figure 5
Correlations between compressive strength and modulus of elasticity of cylindrical specimens of different sizes.

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Table 1
Portland cement properties.

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Table 2
Hydrated lime properties.

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Table 3
Sand properties.

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Table 4
Mortar compositions and environmental conditions during its production.

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Table 5
Results of (4 x 4 x 16) cm prism specimens.

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Table 6
Results of (5 x 10) cm cylindrical specimens.

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Table 7
Results of (10 x 20) cm cylindrical specimens.

Figure 1 Flexural and compressive strength tests with (4 x 4 x 16) cm prism specimens.

Figure 2 Determination of compressive strength and modulus of elasticity of cylindrical specimens.

Figure 3 Curves of compressive strength - water/cement ratio for different kinds of specimen, for mortars with compressive strength in the range of 5 to 20 MPa.

Figure 4 Correlations between compressive strength of specimens of different shapes and sizes.

Figure 5 Correlations between compressive strength and modulus of elasticity of cylindrical specimens of different sizes.

Table 1 Portland cement properties.

Property		Value		Test Method
Density		2.95 kg/dm³		ABNT NBR NM 23 ¹²12 Brazilian Association of Technical Norms (ABNT). NBR NM 23 - Portland cement and other powdered material - Determination of density. Rio de Janeiro: ABNT; 2000.
Fineness		4.00%		ABNT NBR 11579¹³13 Brazilian Association of Technical Norms (ABNT). NBR 11579 - Portland cement - Determination of fineness by the 75 µm (nº 200) sieve - Method of test. Rio de Janeiro: ABNT; 2013.
Setting times	Initial	2h30min		ABNT NBR NM 65¹⁴14 Brazilian Association of Technical Norms (ABNT). NBR NM 65 - Portland cement - Determination of setting times. Rio de Janeiro: ABNT; 2003.
	Final	3h55min
Soundness	Cold	0 mm		ABNT NBR 11582¹⁵15 Brazilian Association of Technical Norms (ABNT). NBR 11582 - Portland cement - Determination of soundness by the Le Chatelier method - Method of test. Rio de Janeiro: ABNT; 2012.
	Hot	0 mm
Compressive strength	3^th day test	26.9 MPa	C.V.^* * C.V.: Coefficient of variation (%) = 1.41 %	ABNT NBR 7215¹⁶16 Brazilian Association of Technical Norms (ABNT). NBR 7215 - Portland cement - Determination of compressive strength. Rio de Janeiro: ABNT; 1996. Corrected version: 1997.
	7^th day test	32.2 MPa	C.V.^* * C.V.: Coefficient of variation (%) = 1.42 %
	28^th day test	34.5MPa	C.V.^* * C.V.: Coefficient of variation (%) = 0.54 %

^*
C.V.: Coefficient of variation (%)

Table 2 Hydrated lime properties.

Property	Value	Test Method
Density	2.32 kg/dm³	ABNT NBR NM 23¹²12 Brazilian Association of Technical Norms (ABNT). NBR NM 23 - Portland cement and other powdered material - Determination of density. Rio de Janeiro: ABNT; 2000.
Water retention	>70%	ABNT NBR 9290¹⁷17 Brazilian Association of Technical Norms (ABNT). NBR 9290 - Hydrated lime for mortars - Determination of water retention - Method of test. Rio de Janeiro: ABNT; 1996.
Non-hydrated oxides	0%	ABNT NBR 6473¹⁸18 Brazilian Association of Technical Norms (ABNT). NBR 6473 - Caustic lime and hydrated lime - Chemical analysis. Rio de Janeiro: ABNT; 2003.
Carbonic anhydride	< 10%
Total oxides	> 90%

Table 3 Sand properties.

Property	Value	Test Method
Maximum diameter	4.8 mm	ABNT NBR NM 248¹⁹19 Brazilian Association of Technical Norms (ABNT). NBR NM 248 - Aggregates - Sieve analysis of fine and coarse aggregates. Rio de Janeiro: ABNT; 2003.
Fineness modulus	2.79
Bulk specific gravity	2.65 kg/dm³	ABNT NBR NM 52²⁰20 Brazilian Association of Technical Norms (ABNT). NBR NM 52 - Fine aggregate - Determination of the bulk specific gravity and apparent specific gravity. Rio de Janeiro: ABNT; 2002.
Unit weight	1.40 kg/dm³	ABNT NBR NM 45²¹21 Brazilian Association of Technical Norms (ABNT). NBR NM 45 - Aggregates - Determination of the unit weight and air-void contents. Rio de Janeiro: ABNT; 2006.
Material finer than 75 µm sieve	0.90%	ABNT NBR NM 46²²22 Brazilian Association of Technical Norms (ABNT). NBR NM 46 - Aggregates - Determination of material finer than 75 µm sieve by washing. Rio de Janeiro: ABNT; 2003.
Water absorption	0.80%	ABNT NBR NM 30²³23 Brazilian Association of Technical Norms (ABNT). NBR NM 30 - Fine aggregate - Test method for water absorption. Rio de Janeiro: ABNT; 2001.

Table 4 Mortar compositions and environmental conditions during its production.

Mortar	PC : lime : sand (mass)	Water/ cement ratio	Humidity	Temperature	Flow (mm)
Mortar	PC : lime : sand (mass)	Water/ cement ratio	(%)	(ºC)	D1	D2	D3	Mean
T1	1.00 : 0.45 : 7.48	1.49	70	26.1	218	216	221	218
T2	1.00 : 1.32 : 6.06	1.43	79	20.0	223	225	229	226
T3	1.00 : 0.32 : 5.25	1.07	79	26.0	212	210	215	212
T4	1.00 : 0.88 : 4.49	1.14	71	19.0	235	240	244	240
T5	1.00 : 0.20 : 3.39	0.74	72	26.3	230	233	228	231

Table 5 Results of (4 x 4 x 16) cm prism specimens.

Mortar	Indirect tensile strength f_t				Compressive strength f_c
Mortar	Number of specimens	f_{t average} (MPa)	Standard deviation (MPa)	Coefficient of variation (%)	Number of specimens	f_{c average} (MPa)	Standard deviation (MPa)	Coefficient of variation (%)
T1	6	1.7	0.15	9.12	12	5.9	0.41	6.85
T2	6	2. 6	0.01	0.15	12	7.0	0.42	6.11
T3	6	3.0	0.33	10.74	12	9.4	0.91	9.76
T4	6	2.9	0.32	11.11	12	10.4	0.31	2.93
T5	6	4.8	0.37	7.70	12	17.1	1.18	6.90

Table 6 Results of (5 x 10) cm cylindrical specimens.

Mortar	Compressive strength f_c				Static modulus of elasticity E_m
Mortar	Number of specimens	f_{c average} (MPa)	Standard deviation (MPa)	Coefficient of variation (%)	Number of specimens	E_{m average} (GPa)	Standard deviation (GPa)	Coefficient of variation (%)
T1	3	5.8	0.10	1.70	3	9.5	0.60	6.38
T2	3	7.1	0.31	4.29	3	12.1	2.44	20.12
T3	3	11.1	0.86	7.75	3	14.0	0.37	2.65
T4	3	12.2	0.55	4.53	3	14.2	0.75	5.24
T5	3	20.7	0.73	3.55	3	19.4	0.42	2.18

Table 7 Results of (10 x 20) cm cylindrical specimens.

Mortar	Compressive strength f_c				Static modulus of elasticity E_m
Mortar	Number of specimens	f_{c average} (MPa)	Standard deviation (MPa)	Coefficient of variation (%)	Number of specimens	E_{m average} (GPa)	Standard deviation (GPa)	Coefficient of variation (%)
T1	3	4.8	0.03	0.68	3	9.6	0.77	8.02
T3	3	10.8	0.89	8.21	3	15.2	0.20	1.33
T5	3	17.3	0.75	4.35	3	18.9	0.86	4.54

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Effect of Specimens' Shape and Size on the Determination of Compressive Strength and Deformability of Cement-lime Mortars

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[1] *e-mail: rcassia.alvarenga@gmail.com